Dyer’s woad Other common names: Asp of Jerusalem USDA symbol: ISTI Isatis tinctoria ODA rating: B
Introduction: Dyer’s woad is native to Europe. It was introduced to Virginia in colonial times as a source material for making of blue dye. Though Eastern U.S. distribution is spotty it is far more widespread in the western states. It survives as an annual, biennial or short-lived perennial depending on conditions.
Distribution in Oregon: There are multiple historic sites scattered throughout Oregon that have been eradicated. Currently, Klamath and Lake Counties have the most infested acres.
Description: Dyer's woad grows up to three feet tall from a thick taproot that extends up to five feet deep. Multiple stems arise from the base sporting foliage having a distinctive blue-green cast with whitish glaze. The upper leaves are smaller and clasp the stem with ear-like projections. Flowers are bright yellow, small and in highly visible clusters in the spring. Flowers have four spoon shaped petals. Fruit pods are flat and black or purplish brown. The most vigorous populations occur mainly in sandy, gravelly soils, and in marginal farmlands.
Impacts: Dyer's woad forms dense colonies in rangelands crowding out native vegetation. This plant is highly competitive, thriving in waste areas, gravel pits, road sides, pastures, field edges, and disturbed soils. It reduces forage availability by suppressing grasses and has low palatability for grazing animals. It is allelopathic.
Biological controls: There are currently no biological control agents available for this plant.
Oregon Department of Agriculture Noxious Weed Control Program Photos by Bonnie Rasmussen, 635 Capitol Street NE Salem, OR 97301 503-986-4621 Bob Barrett, ODA; Steve Dewey, UTU, Bugwood.org www.oregon.gov/ODA/programs/Weeds/Pages/Default.aspx